Hypercholesterolemia in Cardiac Function, Survival and Repair

描述(由申请人提供)：越来越多的机制和翻译研究支持使用基于细胞的治疗来修复被梗塞破坏的心肌组织并恢复心功能。在心肌梗死(MI)和心力衰竭的动物模型中，成体原始细胞群的几个表型不同的亚群被证明可以改善心脏结构和功能。干细胞治疗的小型临床试验总结了这些对缺血性心肌病患者的有益效果。最近发现的心脏干细胞(CSCs)为心脏修复/再生干细胞疗法的发展带来了巨大的希望，因为CSCs天生就具有重建心脏组织的能力。在最近的研究中，我们发现，无论是急性或慢性心肌梗死大鼠，还是慢性心肌梗死猪，冠状动脉内注射CSCs都能改善心功能并再生新的心肌细胞。然而，需要心脏修复治疗的人类患者通常具有一系列心血管危险因素，如高胆固醇血症(HC)、糖尿病、高血压等。随着最近患者对细胞治疗的兴趣激增，了解这些危险因素对细胞介导的心脏修复的影响是很重要的。特别是，HC是一种高度流行的危险因素，并导致一系列病理生理后果。因此，本提案的总体目标是研究HC对CSC介导的心脏修复的影响。我们的基本假设是，根据具体情况，胆固醇在CSC介导的心脏修复中可能是有益的，也可能是有害的。我们认为，轻微的血浆胆固醇升高或氧化程度最低的低密度脂蛋白-胆固醇的存在对心肌和CSCs都是预适应；由此产生的预适应心肌微环境和预适应CSCs增强的旁分泌信号机制共同作用于增强CSC介导的心脏修复。我们进一步认为，血浆胆固醇的显著升高或完全氧化形式的低密度脂蛋白-胆固醇的存在会引发对CSCs和心肌的氧化损伤，导致心脏修复细胞疗法的无效。我们将在三个特定的目标下测试这些假设，使用体外培养的CSCs和存在不同修饰的低密度脂蛋白的心肌细胞，以及具有不同血浆胆固醇水平的在体MI大鼠模型。目的1将确定HC在体内对CSC介导的心脏修复的影响；目的2将在体外确定低密度脂蛋白对CSC功能和修复能力的影响；目的3将确定体外用不同修饰的低密度脂蛋白预先处理CSCs是否会改变体内心脏修复治疗的效果。鉴于血浆胆固醇是一种可改变的危险因素，但对细胞功能也是必不可少的，了解这种普遍存在的危险因素对干细胞治疗的影响将具有翻译和机制上的重要性。该项目将为具有心血管危险因素的患者开发基于细胞的心脏修复疗法的迫切需要的临床前框架提供新的见解。

DESCRIPTION (provided by applicant): Mounting mechanistic and translational studies support the use of cell-based therapies to repair myocardial tissue destroyed by infarction and to restore cardiac function. Several phenotypically distinct subsets of adult primitive cell populations have been shown to improve cardiac structure and function in animal models of myocardial infarction (MI) and heart failure. Small clinical trials of stem cell therapy have recapitulated these beneficial effects in patients with ischemic cardiomyopathy. Recent discovery of cardiac stem cells (CSCs) has sparked intense hope for the development of promising stem cell therapies for cardiac repair/regeneration because CSCs are inherently programmed to reconstitute cardiac tissue. In recent studies, we found that intracoronary delivery of CSCs to rats with either acute or chronic MI and to pigs with chronic MI ameliorated cardiac function and regenerated new cardiac cells. However, human patients needing cardiac reparative therapies generally possess an array of cardiovascular risk factors such as hypercholesterolemia (HC), diabetes, hypertension etc. With the recent surge of interest in cell therapies for patients, it is important to understand the impact of these risk factors on cell-mediated cardiac repair. In particular, HC is a highly prevalent risk factor and contributes to a range of pathophysiological consequences. Hence, the overall goal of this proposal is to investigate the impact of HC on CSC-mediated cardiac repair. Our fundamental hypothesis is that depending on the specific conditions, cholesterol can be beneficial or detrimental in CSC-mediated cardiac repair. We propose that mild elevations of plasma cholesterol or the presence of the minimally oxidatively modified form of LDL-cholesterol precondition both the myocardium and the CSCs; the resulting combination of a primed myocardial microenvironment for cell engraftment and enhanced paracrine signaling mechanisms of preconditioned CSCs work in concert to enhance CSC-mediated cardiac repair. We further propose that marked elevations of plasma cholesterol or the presence of the completely oxidized form of LDL- cholesterol provoke oxidative injury to both the CSCs and the myocardium, leading to loss of efficacy of cell therapies for cardiac repair. We will test these hypotheses under 3 specific aims using both in vitro cultured CSCs and cardiomyocytes in the presence of differently modified LDLs and in vivo rat models of MI with different levels of plasma cholesterol. Aim 1 will determine the effects of HC on CSC-mediated cardiac repair in vivo; Aim 2 will determine the effects of LDLs on CSC function and reparative capability in vitro; and Aim 3 will determine whether pretreatment of CSCs with differently modified LDLs in vitro alters the efficacy of cardiac reparative therapy in vivo. Given that plasma cholesterol is a modifiable risk factor, but is also essential for cellular function, understanding the effects of this prevalent risk factor on stem cell-based therapies will have translational and mechanistic importance. This project will provide novel insights into a much-needed preclinical framework to develop cell-based therapies for cardiac repair in patients with cardiovascular risk factors.